Amplifier for talking machines and like sound-reproducing apparatus



c. E. c. J. MANBY sept. 3, 1929.

AMPLIFIER FOR TALKING MACHINES AND LIKE SOUND REPRQDUCING APPARATUS Fzlsdv lay 18, 1927 Patented Sept. 3, 1929.

UNITED STATES CHARLES EVELYN CREASY JENSEN MANBY, OF HAWKSBURN, VICTORIA, AUSTRALIA.

AMPLIFIER FOR TALKING MACHINES AND LIKE SOUND-REPRODUCING APPARATUS.

Application led May 18, 1927, Serial No. 192,368, and in Australia May 26, 1926.

This invention relates to amplifiers for sound reproducing apparatus, and whilst being particularly applicable to talking machine amplifiers is also applicable to amplifiers or loud speakers for radio broadcasting purposes.

With the majority of existing amplifiers, it is not possible to obtain true reproduction of both high and low pitched musical notes, or sounds having high and low frequency vibrations. I have observed that whilst existing amplifiers are generally satisfactory in the reproduction of notes and sounds ranging in pitch from about the C below7 middle' C of the pianoforte scale and upwards, they do not furnish the best results for notes and sounds which are lower in pitch, the vibrations of such comparatively low pitched sounds or notes becoming blurred and weakened through their passagethrough the amplifier so that the sound emitted therefrom lacks strength and clarity of tone.

The primary object of the present invention is to overcome the objections above referred to by the provision in an amplifier of simple and effective means whereby comparatively low pitched notes or sounds (or sounds of low frequency vibration) as well as comparatively high pitched notes or sounds (or sounds of high frequency vibration) may be reproduced with perfect fidelity as to tonal strength and clarity.

The invention is characterized primarily in that the amplifier or horn is provided with multiple top and/or bottomv walls spaced apart to form a resonance chamber or chambers adjacent the amplifier sound passage, said multiple walls being extended'sidewardly beyond or overhanging the side walls of the amplifier sound passage.

Each said resonance chamber between adjacent multiple walls of the amplifier sound passage is preferably closed at or near the side edges of the respective multiple walls so that the resonance chambers also extend beyond or overhang the side walls of the amplifier and render the latter adequately responsive to the passage of low as well as high pitched sounds which are consequently emitted from the amplifier with alltheir original attributes.

By the invention, I find that the effective note or pitch range of an amplifier can be increased by morerthan two complete octaves whilst, atthe same time, the tonal effect obtained in reproduction throughout this increased range is greatly improved. Moreover, by employing the improved amplifier in the reproduction of orchestral and choral music the various tones of different instruments and voices are distinctly rendered with all their original characteristics.

Referring to the drawings which form part of this specication:

Figure 1 is a cross section of an amplifier provided with multiple top and bottom walls and resonance chambers projecting sidewardly beyond the side walls of the amplifier sound passage in accordance with the invention.

Figure 2 is a longitudinal section of an amplifier according to the present invention, mounted within a talking machine cabinet and operatively connected to a tone arm.

Figure 3 is a front view of Figure 2 the front wall of the cabinet being omitted.

Figure 4 is a plan of an amplifier embodying the present improvements.

Figure 5 is a cross section of the amplifier taken on the line V-V of Figure 2.

Referring to the drawings the numerals 2, 3 indicate sound boards or plates which are disposed contiguous to and spaced outwardly from the lower and upper walls 4, 6, of the sound passageway 7 through the amplifier, thereby forming, in effect, double or multiple walls enclosing resonance chambers 8, 9, which are disposed adjacent or contiguous to said sound passageway.

According to the present invention, the multiple walls, comprising the sound boards 2 and 3 and the contiguous lower and upper walls 4 and 6 of the amplifier, are extended for a relatively great distance sidewardly beyond the amplifier 'side walls 11, 12 as indicated at 13, whilst suitable distance pieces or side closures 14 extend between the adjacent multiple walls at the side edges thereof. By this construction the multiple walls and the resonance chambers 8, 9, are provided with wing portions, indicated at 16, 17 which extend sidewardly beyond or overhang the side walls 11, 12, of the amplifier sound passage 7, said wing portions of the resonance chambers being closed at or near the side edges of the multiple walls 2, 3, 4 and 6. The side walls 11, 12 preferably converge rearwardly at such an angle to the side edges of the wing portions 16, 17 that the width of the latter increases from front to rear of the amplifier.

By thus extending the multiple walls and the resonance chambers sidewardly beyond the upstanding side walls 11, 12 of the sound passage, the effective note or pitch range of the amplifier is greatly augmented and thek The improved amplifier is adapted for connectiony to atone arm 19 or other sound reproducer andfor this purpose a mounting plate20 having an aperture 21 may be affixed to the amplier so that said aperture 21 registers with the inlet end of the sound passageway 7. The mount-ing plate 2O may be secured by screws or the like to a suitable supporting structure as at 22, so that communication is established between the reproducer and the sound passageway ofthe amplifier.

The upstanding side walls 11 and 12 may diverge forwardly from each other whilst the lower` and upper walls 2, 3, 'may be shaped so that the sound passageway 7 extends downwardly and forwardly from its inlet end the upper walls being curved or inclined upwardly and forwardly adjacent the outlet end,v

of the amplifier as seen in Figure 2, lt may not be necessary to continue the upper sound board or wall 3 for the entire length' of the amplifier, in which instance said sound board may terminate some distance rearwardly of the front of the amplifier as indicated at 25 (Figures 2, 3 and 4). Each resonance chamber may be entirely open at its front end, as indicated at 30 in Figure 2 or said front end may be closed in which case one or more holes of suitable size and shape may be formed through the front portion of each sound board or plate 2, 3, or the walls 4, 6.

In addition to the longitudinally extending distance pieces or side closures 14 for the resonance chambers, rear transverse distance pieces or closures 26 may extend between the respective double walls.2. and 4, 3 and 6, at the rear transverse edgesthereof. Supplementary distance pieces or spacers 27 may be provided where desired as shown.

The amplifier may be composed of any suitable material but woodis considered preferable. The double walls 2, 3, 4 and 6 may be of multiple ply wood. The various walls and parts of the amplifier may be fastened together by glue or other adhesive and/or by tacks, nails or the like.

if desired two ory more of the resonance chambers 8, 9 may be formed in contiguous superposed relationship ,externally of theupper and/or the lower walls 6, 4 of the sound passage.

Having now described my invention what I claim as new and desire to secure by Letters Patent is 1. An amplifier for sound reproducing apparatus comprising upper and lower walls and side walls to form a sound passage, one or more sound boards disposed adjacent to and spaced outwardly from the upper and lower walls of the amplifier so as to provide double or multiple walls the spaces between which form resonance chambers, said multiple walls at the top and bottom of the amplifier being extended sidewardly beyond the side walls of the amplifier so as to formv wing portions which overhang or project beyond said side walls, the said wing portions covering a larger area than the sound passage.

2. An amplifier for sound reproducing apparatus comprising upper and lower wall-s and side walls to form a sound passage, one or more sound boards disposed adjacent to and spaced outwardly from the upper and lower walls of the amplifier so as to provide double or multiple walls the spaces between which form resonance chambers, said multiple walls being extended sidewardly beyond the side walls of the amplifier so as to form wing portions which overhang or project beyond said side walls, the said wing portions covering a larger area than the sound passage, said lspaces between the multiplek walls being closed at the side edges thereof so that the resonance chambers also extend side-wardly beyond the side walls of the sound passage.

3. An amplifier for sound reproducing apparatus comprising khollow top and bottom walls and side walls forming a sound passage, the .spaces within the hollow top and bottom walls forming resonance chambers which are closed adjacent the side edges of said hollow walls and extend sidewardly for a considerable distance beyond the side walls of the amplifier sound passage, the said wing portions covering a larger area than the sound passage. Y i

4. An amplier for sound reproducing apparatus comprising in combination vertical side walls, horizontal top vand bottom walls extending between and secured to said side walls forming a sound passage, one or both of said horizontal walls being composed of two relatively thin sheets of material which are spaced at a relatively slight distance apart so as to form therebetween a resonance chamber which adjoins, but is isolated from the amplifier sound passage, said sheets having wing portions which project sidewardly beyond said vertical side walls, the said wing portions covering a larger area than the sound passage, and` distance pieces extending longitudinally of the amplifier between each spaced pairjof said sheets adjacent the sideedges of the latter whereby the sides of the resonance chamber are closed at points outwardly removed from said Vertical walls substantially as describe-d.

5. An amplifier for sound reproducing apparatus comprising vertical side walls which converge rearwardly, horizontal top and bottom walls extending between and secured to said side walls and forming therewith a sound passage, said horizontal walls being composed of two relatively thin sheets of material which are spaced at a relatively slight distance apart so as to form therebetween a resonance chamber which adjoins the amplifier sound passage, said sheets having wing portions which project sidewardly beyond said vertical side Walls of the sound assage, the said wing portions covering a arger area than the sound passage, said resonance chamber being closed adjacent the edges of said wing portions.

In testimony whereof I aix my signature.

CHARLES EVELYN CREASY JENSEN MANBY. 

